502 PHANEROGAMS. 



and absorb their nourishment from it, their basal parts and the intermediate plumule 

 are pushed out of the seed. The portion of the axis which bears the cotyledons, 

 as well as that which developes above them, remains very short, but a consider- 

 able lateral increase of size takes place beneath the apex, due to a large develop- 

 ment of parenchymatous tissue. The stem thus acquires the form of a roundish 

 tuber, which it retains even at a later period in some species ; but in most it 

 lengthens in the course of years into an erect tolerably stout colunm which some- 

 times attains a height of some metres. This slow increase in height, together with 

 the considerable increase in thickness of the growing end, is correlated with the 

 absence of a tendency to branch as in other similar cases (Isoe/es, Ophioglossum, 

 Aspidium Filix-mas, &c.). The stem of Cycadeae usually remains perfectly simple, 

 although old stems sometimes divide into branches of equal stoutness. But when 

 several flowers are formed at the summit, this evidently depends on branching ; and, 

 as far as one is able to judge from drawings, it is probable that this branching 

 is dichotomous. In old or sickly plants small bulbous or tuberous gemmae are not 

 unfrequendy found at the base of the stem under or above ground, the morphological 

 nature of which is still doubtful ; in Miquel's opinion it is not impossible that they 

 spring from old leaf-scales, and have therefore nothing to do with the branching of 

 the stem. 



The whole of the surface of the stem is furnished with leaves arranged 

 spirally ; no internodes can be distinguished. The leaves are of two kinds ; dry, 

 brown, hairy, sessile, leathery scales of comparatively small size, and large, stalked, 

 pinnate or pinnatifid foliage-leaves. The scales and the foliage-leaves alternate 

 periodically ; a rosette of large foliage-leaves is produced annually or biennially, and 

 among these the terminal bud of the stem is enveloped with scales, under protection 

 of which the new whorl of foliage-leaves is slowly formed. This alternation begins 

 at once on germination in Cycas and other genera, a number of scale-leaves follow- 

 ing the leaf-like cotyledons, and enveloping the bud of the seedling ; after these a 

 pinnate though small foliage-leaf is then usually developed, which is again followed 

 by scales. It is only as the strength of the plant increases after several years' 

 growth that the foliage -leaves are produced in whorls constantly increasing in size, 

 and forming, after the older ones have died off, the palm-like crown of leaves, the 

 scales which stand above them enclosing at the same time the apical bud of the 

 stem. In this bud the foliage-leaves are so far formed beforehand, that when they 

 at length burst the bud they only have to unfold, this process then occupying only a 

 very short time, while one or two years elapse before the unfolding of the next 

 rosette of leaves. The leaves which proceed from the bud are in Cycas and other 

 genera circinate like those of Ferns ; in others the rachis of the leaf only is rolled 

 up ; in others, finally, as Dion^ the growth of the leaf is straight, its lateral leaflets 

 being also straight before expansion \ The unfolding is, as in Ferns, basifugal, and, 

 probably in consequence of this, there is also a permanent apical growth and a basi- 

 fugal development of leaflets. The leaflets are usually simple, and generally stand 

 alternately on the rachis, which is often i to 2 metres long. The mode in which 



* [This statement is not quite exact. In Zamia and Encephalartos the leaves are not circinate in 

 vernation ; and even in Cycas it is only the leaflets and not the rachis that is so.] 



